Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $54.92   11.158%   $61.048   $61.05   $61.05   $61.00  
  Purchase #2 $230.66   4.172%   $240.2831   $240.28   $240.30   $240.30  
  Purchase #3 $158.29   5.704%   $167.3189   $167.32   $167.30   $167.30  
  Purchase #4 $88.29   9.492%   $96.6705   $96.67   $96.65   $96.70  
  Purchase #5 $83.82   9.703%   $91.9531   $91.95   $91.95   $92.00  
  Purchase #6 $89.62   8.263%   $97.0253   $97.03   $97.05   $97.00  
  Purchase #7 $43.50   13.445%   $49.3486   $49.35   $49.35   $49.30  
  7 purchase totals = $749.10       $803.6475   $803.65   $803.65   $803.60